1. Field of the Invention
The invention relates to an electronic unit for measuring operating parameters of a vehicle wheel, comprising an electronic module and an inflation valve.
2. Description of the Related Art
An increasing number of motor vehicles possess systems for monitoring and/or measuring parameters including sensors.
By way of example with respect to such systems, mention may be made of the systems for monitoring the pressure of tires including electronic modules mounted on each of the wheels of the vehicles, dedicated to the measurement of parameters such as the pressure and/or temperature of the tires fitted to these wheels, and intended to inform the driver of any abnormal variation in the measured parameter.
One of the existing solutions most commonly used to ensure the attachment of the electronic modules on the rims of the wheels involves the provision of electronic units each composed of an electronic module assembled together with an inflation valve allowing said electronic module to be secured on the rim of the wheel.
One solution relating to such electronic units involves the provision of specific inflation valves capable of ensuring the transmission of the forces to which the electronic modules are subjected. However, this solution has proven to be expensive because, in addition to the high price of the inflation valves, which are generally made entirely of metal, it also requires the provision of ancillary parts (nuts, sealing gaskets, etc.) specially designed to guarantee a sealed attachment of the inflation valves on the rims.
With a view to overcoming this drawback, a second solution has involved the provision of the inflation valves in an elastomeric material, having the same basic design as the traditional inflation valves of the “snap-in” type, modified in such a way as to ensure the absorption of the forces to which the electronic modules are subjected.
This solution has resulted in particular in the provision of an electronic unit as described in patent application WO2009/007035 comprising:                an electronic module,        an inflation valve of the “snap-in” type including:                    a valve body in an elastomeric material, provided with a longitudinal axial bore and intended to extend through an orifice arranged in the rim, said valve body being composed of an elastically deformable trunk and an abutment head against the rim, separated from the trunk by a collar adapted to be positioned in a sealed manner in the orifice arranged in said rim,            and a hollow tubular core made of a rigid material, accommodating a covering mechanism and having dimensions adapted for it to be accommodated in the bore of the valve body and to extend to either side in the continuation of said valve body, said tubular core being constituted by two longitudinal sections arranged one in relation to the other and relative to the valve body, in such a way as to allow an elastic deformation of the trunk capable of permitting the installation of the inflation valve through the orifice of the rim,                        and means for connecting the electronic module and the inflation valve comprising:                    a ring connected to the electronic module adapted to be mounted in a sliding manner around the portion of the tubular core extending in the continuation of the abutment head of the valve body, in a position of the electronic module where the latter extends in the direct continuation of the inflation valve,            and means of assembly by the fitting of a hollow sleeve connected to the ring of the electronic module in the interior of an annular chamber arranged in the abutment head of the valve body.                        
In view of these particular characteristics, and in practice, such an electronic unit has the added advantage of guaranteeing a behavior of the inflation valve similar to that of a traditional inflation valve of the “snap-in” type.
On the other hand, according to this principle, the assembly of the electronic module and of the valve body is accomplished with the help of a connection of the sleeve fitting type, the resistance of which is linked directly to the resistance to stretching of the elastomeric material of the inflation valve. This connection should, in fact, be of a removable nature with a view in particular to permitting the electronic module to be recovered in the event of damage to the inflation valve. As a result, it is very difficult to arrive at a compromise between the resistance, on the one hand allowing the removal of the two elements, and on the other hand guaranteeing the durability of the connection at the high speeds of the vehicles. For this reason and in practice, the electronic units include an additional removable locking device of the type described in the patent application WO2009/007035, being an elastic ring, a spring ring of the “lyre” type, an “O-clamp” crimping collar, a screw clamp, or various types of locking key. However, these additional devices require specific tooling for the purpose of their positioning and their retraction, with the result, furthermore, that the stages of installation and removal of the electronic units become more complex.
With a view to overcoming this drawback, a solution as described in particular in patent FR 2 954 733 has involved the provision of an electronic unit equipped with a locking device guaranteeing a very high resistance to pulling out of the electronic module, but not requiring additional time.
For this purpose, this electronic unit comprises:                an inflation valve including, on the one hand, a valve body intended to extend through an orifice arranged in a wheel rim, and composed of a trunk and an abutment head against the rim, and, on the other hand, a rigid hollow tube extending in the continuation of the abutment head,        an electronic module secured to a ring adapted to be mounted in a sliding manner about the rigid tube,        and means for securing the electronic module and the inflation valve, comprising means of locking including:                    transverse notches arranged on the periphery of the rigid tube,            and a plate latch associated with the electronic module and exhibiting a locking tooth adapted to be accommodated in a transverse notch of the rigid tube, in such a way as to ensure the locking in translation of said electronic module relative to said rigid tube, said plate latch:                            being mounted on the electronic module with a possibility of deflection between a position of locking in which the locking tooth is engaged in a notch in the rigid tube, and a position of unlocking in which the locking tooth allows a relative displacement in translation of the electronic module relative to the rigid tube,                being associated with elastic means adapted, in the absence of loads, to apply to this plate latch a force for maintaining the latter in its position of locking, and, during an influence exerted on these elastic means, in order to bring about a displacement of this plate latch towards its position of unlocking.                                                
According to this solution, the locking of the electronic module on the inflation valve is thus assured by a plate latch being maintained in a natural locking position by elastic means, and designed to be switched towards an unlocking position by a simple influence exerted on said elastic means.
As a result, the locking means provide rigid locking of the electronic module on the rigid tube of the inflation valve, thereby guaranteeing a very high resistance to pulling out of said electronic module.
Such a solution has a major drawback, however, likewise resulting from the necessity to possess special tooling in order to guarantee, at the time of installation of the electronic unit on rims having different thicknesses, that the notch in which the locking tooth is accommodated consists of the accessible notch situated closest to the abutment head, which alone is capable of permitting high performances of the inflation valves to be guaranteed, in particular in terms of longevity and sealing.
Whereas the automobile manufacturers routinely possess such tooling, the same does not apply to the garages that are called upon in particular to replace damaged inflation valves, and the risks of imperfect assembly resulting in a notable impairment of the performance of the new inflation valve are not negligible.